There's an off-site available in St-Therese (clicky) that will store a little less expensively than what you quote above (OR, store you most precious goods off-site and rack the ones you won't worry about in the basement). I know the cellar and can attest to the fact that it is indeed an excellent place for perfect storage, both for temp/humidity and security. To me, this type of set-up would be the most secure and give you a lot of 'piece of mind'. It's not the temperature stability that concerns me in your present home. Icewino brings up a very valid concern (flooding/freezing). Your tenants won't have near the level of concern on your items as you would in the event this happens and you're way too far away to begin to deal with it.